People familiar with the benefits of high pressure fluid systems having long desired higher pressure pumps which are cost effective to power such systems. In the cleaning industry, for example, fluid gun operators have recognized for years the enhanced benefits of cleaning with fluid pressure in excess of 12,000 PSI. Systems capable of operating at 20,000 PSI or even 40,000 PSI are being seriously considered for cleaning applications, and those skilled in the hydroblasting art appreciate the substantially enhanced capability of such higher pressure systems.
A significant problem with obtaining such higher fluid pressures on a commercial basis relates to the cost and life of the fluid pump. Pumps with a plurality of plungers are commonly used for obtaining high pressures, and such high pressure pumps preferably utilize an inline valve pump design, as disclosed in U.S. Pat. No. 4,551,077, for generating high fluid pressure without causing significant metal fatigue which leads to pump failure. As the maximum output pressure from the inline pump increases, increased difficulties are encountered in the operation of placing the pump compression rods under the desired axial load. A plurality of these rods (typically four) are conventionally provided exterior of the pump chamber, and provide the desired compressive force to reliably seal the pump housing to the outlet housing. The rods are typically threaded for receiving corresponding nuts, and large powered wrenches have been employed to torque such nuts to the extent desired to produce a high compressive force. This desired compressive force maintains sealing between the pump housing and the outlet housing, which may comprise a pump discharge housing and a suction valve seat member. Powered wrenches, in turn, have their own capacity limitations, and are a significant drawback to the low cost maintenance and repair of a pump, since pump operators frequently do not have the necessary wrenches to torque the nuts to the extent recommended by the pump manufacturer. Hydraulic nuts have been proposed to place threaded rods under a significant load to produce a necessary compressive force, but these hydraulic nuts are expensive, and their utilization requires a fluid power source that may not be available.
As a consequence, some high pressure pumps fail because of leakage between the pump housing and the pump outlet housing, wherein the leakage is attributable to the failure to provide the necessary torque on one or more of the nuts that cooperate with the plurality of pump compression rods. To overcome this problem, some maintenance personnel have utilized larger and more expensive wrenches to torque the nuts, and in some instances have applied substantially more torque to the nuts than recommended by the pump manufacturer. In these cases, the compression rods are subjected to a substantially higher axial load than desired, which contributes to fatigue and failure of pump components. Due to the substantial forces involved, failure of a compression rod may cause significant damages to the pump and adjacent equipment, and more importantly may cause injury or death to personnel.
Improved methods and apparatus are required to facilitate the manufacture and repair of a high pressure pump in a manner that will subject pump compression rods to the necessary load required to seal the pump housing with the outlet housing, but will not overload these compression rods and thereby decrease the life of the pump. Pump life can be substantially enhanced according to the techniques of the present invention, while repair and maintenance costs for a pump are reduced since both the time and the equipment required to disassemble and reassemble a high pressure pump are significantly reduced.
The disadvantages of the prior art are overcome by the present invention, and an improved pump and a method of axially loading pump compression rods are hereinafter disclosed that will significantly contribute to the desire for a relatively low cost, high pressure pump.